I tackled this one recently myself (more TTPs actually). I did not find an actual guide (which probably would have saved a pile of time). I did end up ape'ing the Land Ops SOPs (much like you intend).
Some formatting tips from my own expereince. If they are going to be wide spread SOPs and translated into a bilingual format, use the "Insert Table" function in MS Word, creating two columns and a bunch of rows (can always add more rows later). When it is pre-formatted for translation, it makes it easier for other desk jockeys to accept it without a lot of editing later.
Give each paragraph and sub-para it's own box (on the left for English and on the right for French). This will make the document line up in the columns, making the document easier to read.
Normal numbering, lettering of paras and sub paras apply as per military writing (along with the rest of the formatting rules, similar to a very large memoradum).
Keep it short. IMHO SOPS need to be short and sweet. The final product should fit in my pocket if possible (depending on job). Use accepted acronyms throughout (it's a military doc, and not for outside consumption). Generally, there is no need to exand on subjects in SOPs, as that information would be available elsewhere.
A great example would include diagrams, and proformas of applicable reports and returns. Look at the Tactical Aide Memoire (TAM) and the Infantry insert found on AEL for other examples of good SOP type documents. A "TAM" format would also allow you to expand in the future, with inserts, for "sub-jobs".
Not much help, I know... It is what I drafted for myself, pretty much verbatum, when I came up with a revision of TTPs this past spring. Stick to your guns on this, as people will try to insert a lot of unnecessary fluff that they feel is "necessary".
EDIT TO CHANGE: Documentum to AEL